The Effect ECAP Processing Routes on the Microstructure and Mechanical Properties of AISI 316 Austenitic Stainless Steel

In the present study, ECAP process was carried out for 8 passes on a 316 austenitic stainless steel at 350°C using a die with a channel angle of 105°. Microstructure observations with transmission electron microscopy show that route A leads to a finer grain size and a narrower size distribution range than route C. The average grain size was measured to be 188 nm for route A and 254 nm for route C. In addition, due to the high stability of the austenite phase in the studied steel, deformation-induced martensite (DIM) was not observed to form during ECAP using any of the above routes. Based on the X-ray diffraction analysis, the structure after ECAP is completely austenitic. In terms of mechanical properties, route A leads to higher strength and hardness than route C. However, ductility of the material processed by this route is lower than that of route C. Comparing the results of this research with the published results of the same author’s previous research using the route B_C shows that the microstructure obtained from route A is more uniform than the route B_C. Moreover, in comparison with route B_C, the processed material exhibits more suitable combination of high strength and acceptable ductility (YS = 1557 MPa and ε_f = 14.5%).